I agree with the importance of good training however I am not sure I see the level of danger that you are suggesting.

Most countries other than the UK allow power sockets in bathrooms. There doesn't appear to be a higher accident level in these lands.

Many countries have far lower electrical installation standards. On one Chinese building site I complained about a twisted and taped joint in a 400V 3phase cable being out in the rain. They considered this to be resolved by putting an upturned plastic bucket over it.

Solar panels on roofs have two intrinsic risks, working at height, and they can't be switched off, you just have to wait for it to get dark. I would suggest that injurys due to falls from height are much more common than electrical accidents.

What are you considering to be dangerous and are there any accident statistics?

Roger B said:

a) What are the special conditions for DC ELV systems? Current ratings are the same as AC and only as you get above 24V you need to think about arcing when switching.

www.youtube.com/watch

gkenyon said:

short video but it does illustrate some of the points that have been discussed here: www.facebook.com/.../3507234699527923

Yes seen that one, notice the crappy electrical pliers, barely capable of cutting 6mm solar cable.  A proper pair of cable cutters should be essential safety kit, long handle snip thru in a heatbeat.  Its the method of last resort and amateurs dont learn these things (plus PPE of course), gloves, goggles and makes sure your overalls arent flammable with spilt liquids)

Roger B said:

shorting switches would be a better option that isolators a

good way to start a roof fire?

Andy Millar said:

So I think this comes down to: Do we have evidence that the BPEC 0018 Level 3 Award and the underpinning IEC 60364-6, IEC 60364 and IEC 62548 are inadequate to manage the risks? (Noting that BPEC 0018 teaches that the design and equipment must meet those standards). I'm not arguing that they are or aren't

Hi Andy Im not familiar with BPEC (plumbers and gas fitters?).  Cant find much about them or independent credentials. They seem very coy about what their courses offer and no indication of costs?  Looks like the kind of outfit which a large Corp would use for special training for specific site needs?  Not for the Sole trader leccie? Doesnt seem like too much would be devoted to the tangled web of Regs IEC etc.?  Anyone any experience using BPEC .  The CEO is a tradesman plumber.  It has a very professionally convoluted website making a lot of claims which I cant verify as yet.

But I found this

BPEC Award Solar PV Installer & BPEC Electricity Energy Storage Systems Course

£895.00 + VAT

Rob Tes said:

good way to start a roof fire?

Not really.  Solar panels are inherently current limited by the way they work.  In normal operation, they will be run at a current close to their short-circuit current.  So in the case of a short, nothing much happens to the panel, and the wiring needs to be able to handle that current anyway.

Rob Tes said:

Its the method of last resort

Surely this is why BS 7671 requires a means of isolation from every source.

Battery installations use short string interlinks and often have overcurrent protection within, and at the top of, each string ... this, and long runs to combiner boxes, makes the solar PV system very different, and assumptions used to draw analogies between PV arrays and a battery are, in my opinion, flawed.

When we talk about "method of last resort", I'm very mindful of EAWR Reg 14. I'm not sure we have the PV array design right yet ... the risk is not reduced "SFARP" and not enough research has been carried out into isolator fires, "oh well we'll not fit them then" isn't really a good excuse for EAWR Regulation 14 in my opinion.

I should not have to see this method under any circumstances in my opinion ... especially now array voltages are at 1500 V DC ! We can, and MUST have a safer design approach!

Simon Barker said:

So in the case of a short, nothing much happens to the panel, and the wiring needs to be able to handle that current anyway.

Agreed, but it's not just about protection against overcurrent. Arc can still form, or the DC cabling must be made safe to work on.. Detecting it at the inverter end will alert someone to the fault, but if all they can do is cut cables, that's no good !

We must do better and provide a means of disconnecting the source, in line with the requirements of the General Rules of BS 7671, so it's safe to work on cables and connectors which can't be disconnected on-load either .

gkenyon said:

"method of last resort", I'm very mindful of EAWR Reg 14. I'm not sure we have the PV array design right yet ... the risk is not reduced "SFARP"

gkenyon said:

When we talk about "method of last resort", I'm very mindful of EAWR Reg 14. I'm not sure we have the PV array design right yet ... the risk is not reduced "SFARP"

Yes the convoluted EAWR written by lawyers?  I dont see any mention of the "Crowbar" technique.  Isnt this a std method in electrical traction systems for worker protection?

My OP was only concerned with Solar systems for domestic applications and the dangers posed.  We can SFARP if we limit Solar arrays <50Vdc.  IMHO its foolish to allow higher array volts of ca 100V or even 480Vdc (Ive seen on YT probably that Vid posted here)

Facebook

https://www.facebook.com/reel/3507234699527923

I suspect this was several 100Vdc commercial site judging by the length of arc flash

My proposition is to use large knife switches with a gap of ca 50mm for Solar dc<50V.  This system was used in the London underground prewar (600 Vdc).  Its simple and it works. The convenient design of MCBs did away with all the clutter of cast iron re-wireable switch fuse boxes - with their knife switches..

https://vi.aliexpress.com/item/1005003453152419.html?spm=a2g0o.productlist.main.3.5ca41bd96PlNph&algo_pvid=fb3c70a7-cb05-4e87-b7af-a6fa00ac3907&algo_exp_id=fb3c70a7-cb05-4e87-b7af-a6fa00ac3907-1&pdp_npi=4%40dis%21GBP%216.38%216.06%21%21%217.77%21%21%402103853617006671710863788e3ba4%2112000025856398788%21sea%21UK%21929926363%21&curPageLogUid=QOlMH3g17WF6

That humble domestic master switch is a clever robust design - with built-in rewireable strip fuse, (Siemens prewar pattern) and is in use for millions of dwellings in the far east  all for the princely sum of £6  63A rating (could be doubled).  I would trust that..

But roll out the tumbril for I shall be bound for Tyburn Gate and a Public hanging for my heresy.

We can SFARP if we limit Solar arrays <50Vdc. 

Not necessarily - in some ways you're just trading one hazard (higher voltage) for another (higher current).. We're actually quite good at handling several hundred volts around the home (230V a.c. is a bit over 300V pk; and for 3-phase supplies - increasingly common domestically these days - it's over 560V pk) as we generally have the materials and techniques to handle them with adequate safety), especially at modest currents.

My proposition is to use large knife switches

Humm - those simple types need some skill to use safely - fail to open or close them smartly enough and you can cause a lot of damage - from overheating, if not arcing. The less well shielded types risk allowing shorts between exposed parts too.

Detecting it at the inverter end will alert someone to the fault, but if all they can do is cut cables, that's no good !

There's always the option of employing time - wait a few hours and the sun will set

   - Andy.

Rob,

Do you actually understand what you are talking about?

What is a certified and authentic EE ?

Why do you consider that applying a short circuit to a almost constant current supply will cause a roof fire yet a few posts further on suggest a rail traction style crowbar which has the same effect?

I would suggest that rather than YouTube you look at some real information. The guide to ‘Photovoltaics in Buildings’ from the DTI covers most of the points and I would consider it understandable by most competent electricians.

https://files.bregroup.com/solar/Guide_to_the_installation_of_PV_systems_2nd_Edition.pdf

There will always be people who will go for cheap rather than quality but that applies to everything not just Solar PV.

Rob,

Do you actually understand what you are talking about?

What is a certified and authentic EE ?

Why do you consider that applying a short circuit to a almost constant current supply will cause a roof fire yet a few posts further on suggest a rail traction style crowbar which has the same effect?

I would suggest that rather than YouTube you look at some real information. The guide to ‘Photovoltaics in Buildings’ from the DTI covers most of the points and I would consider it understandable by most competent electricians.

https://files.bregroup.com/solar/Guide_to_the_installation_of_PV_systems_2nd_Edition.pdf

There will always be people who will go for cheap rather than quality but that applies to everything not just Solar PV.